Reduced kernel size by 512KB by moving private buffer into cstart() function.
Replaced assertions with erroneous return values. Removed assertions relating
to isuserp(rp), since all processes should become user processes; system
processes are now treated similar to other processes.
when lock timing is enabled in minix/config.h.
Added phys_zero() routine to klib386.s that zeroes a range of memory, and
added corresponding system call.
The call works. Permission check, restriction of outstanding notifications
to be added. Low level code to make it work from within interrupt handlers
will be added as well.